The volume occupied by red cells in a unit of blood is expressed as a percentage known as the hematocrit percent, and must be measured in many diagnostic medical procedures. The measurement is usually performed by separating the red cells from plasma by subjecting a column of blood to centrifugal force. The invention provides a new and useful apparatus for receiving a plurality of columns of blood which is readily adapted to positioning in a centrifuge and which has readily viewable means for directly reading the hematocrit percent.